Scanning Electron Micrograph (SEM) showing kefir microorganisms in a polysaccharide grain; magnified 8000x at 35mm. Kefir is a fermented milk beverage. Kefir grains are a combination of bacteria and yeasts in a matrix of proteins, lipids, and sugars. This symbiotic matrix forms "grains" that resemble cauliflower. Many different bacteria and yeasts are found in the kefir grains, which are a complex and highly variable community of microorganisms such as Saccharomyces kefir, Torula kefir, Lactobacillus caucasicus, Leuconnostoc spp., lactic streptococci as well as lactose-fermenting yeast. Kefir grains contain a water soluble polysaccharide known as kefiran that imparts a rope-like texture and feeling in one's mouth.